P-chiral compound

The rhodium complexes of the ferrocene derivatives 39 have shown useful characteristics for the reduction of itaconates as well as dehydroamino acid derivatives [15, 167-170]. These compounds are hybrids between ferrocene-based ligands and the various other types. The P-chiral compounds, which in some ways are DIPAMP hybrids, showed tolerance for the reduction of N-methyl en-amides to produce N-methyl-a-amino acid derivatives [169-171]. 

Asymmetric synthesis utilizing chiral auxiliaries represents the most effective method for the synthesis of chiral organophosphorus compounds. During the last few years this method has seen significant development [17-20]. Nucleophilic displacement at the phosphoms atom is one of the most popular and efficient methods for the preparation of enantiopure P-chiral compounds. At present, the most commonly used are chiral secondary alcohols/halophosphines [12,13,15,17],... 

Scheme 21 Synthesis of P-chiral compounds 66 via e-desymmetrized aminophosphazenes...

Ortiz [47] recently described the ortho-directed lithiation of R,R-diphenylami-nophosphazenes 64 followed by electrophilic quenching as an efficient process for the preparation of / -chiral ort/io-functionahzed P-chirogenic amidophosphinates 65 in good yields and diastereoselectivities. The usefulness of the method was shown with the preparation under mild reaction conditions of a variety of functionalized P-chiral compounds 66 in high yield and excellent stereoselectivity, including phosphinic esters, amides, thioamides, phosphine oxides, and (2-aminophenyl)phosphine boranes (Scheme 21). 

Efficient and general methods for the synthesis of chiral phosphine oxides and related compounds are a permanent subject for research of organic chemists. Therefore, the application of biocatalytic methods for the preparation of optically active P-chiral compounds has attracted great attention and a number of successful syntheses were described [172-178]. 

Casimiro M, Roces L, Garcia-Qranda S, Iglesias MJ, Lopez Ortiz F (2013) Directed ortho-lithiation of aminophosphazenes an efficient route to the stereoselective synthesis of P-chiral compounds. Org Lett 15 2378-2381... 

Figure 10.29 Optical resolution of P-chiral compounds with hydrolytic enzymes. ...

The rearrangement has also been extended to P-chiral S-phenyl phos-phinothiolate 79 and 0-phenyl phosphinothioate 80 (Scheme 21). With these asymmetric compounds, the C-P bond formation was found to occur stereose-lectively and with retention of configuration at phosphorus [51]. 

Resolution of various racemic P-chiral phosphorylacetates 70 involved the same approach as was shown for sulfinylcarboxylates (Scheme 2). However, unlike the case of sulfinyl compounds, only PEE proved efficient for their P(0) analogues. 

The first P-chiral hydroxy phosphoryl compounds that were enzymatically resolved into enantiomers were o-hydroxyaryl phosphines and their oxides 75. The resolution was achieved via enzyme-assisted hydrolysis of their O-acetyl derivatives 74, the most effective enzymes being CE and Upase from C. rugosa (CRL) (Equation 35). The highest enanfioselectivity was observed in the case of naphthyl derivatives (Equation 36), having a P=0 moiety. ... 

On the other hand, the enantioselective 1,4-addition of carbanions such as enolates to linear enones is an interesting challenge, since relatively few efficient methods exist for these transformations. The Michael reaction of p-dicarbonyl compounds with a,p-unsaturated ketones can be catalysed by a number of transition-metal compounds. The asymmetric version of this reaction has been performed using chiral diol, diamine, and diphosphine ligands. In the past few years, bidentate and polydentate thioethers have begun to be considered as chiral ligands for this reaction. As an example, Christoffers et al. have developed the synthesis of several S/O-bidentate and S/O/S-tridentate thioether... 

Entries 4 and 5 are examples of use of the Sakurai reaction to couple major fragments in multistage synthesis. In Entry 4 an unusual catalyst, a chiral acyloxyboronate (see p. 126) was used to effect an enantioselective coupling. (See p. 847 for another application of this catalyst.) Entry 5 was used in the construction of amphidinolide P, a compound with anticancer activity. 

The reaction of A-Boc protected amino acids alanine (184) and valine (185) with phenyldichlorophosphine in the presence of NEt3 was reported to lead to the clean formation of essentially one compound in each case, the P-chiral, tricoordi-nated, 1,3,2-oxazaphospholidinones 186 and 187 respectively (Scheme 52) [83],... 

A few examples will illustrate the case. The parent trans-diene derivatives 31a and 3235 have nearly planar chromophores, but the Cotton effects are quite strong and opposite in sign (+15 and —27.9, respectively). This can be attributed mainly to the allylic axial C—CH3 bonds, which provide a positive contribution for compounds 31 and a negative for 32. Furthermore, the As values of P-chiral s-trans-31 are strongly dependent on the polarizability of the allylic C—X bond. 

Haynes, R.K., Lam, W.W.-L., and Yeung, L.-L., Stereoselective preparation of functionalized tertiary P-chiral phosphine oxides by nucleophilic addition of lithiated tert-butylphenylphosphine oxide to carbonyl compounds, Tetrahedron Lett., 37, 4729, 1996. 

P-Chiral organophosphorus compounds are of great importance in biological chemistry, organic synthesis and asymmetric catalysis. However, their preparations usually require tedious steps. (-)-Menthyl phenylphos-... 

Significant progress has been witnessed in asymmetric catalysis/ In conventional asymmetric catalysis, the asymmetric catalyst C provides the enantioenriched product P, whose structures are generally different from those of the asymmetric catalysts. In contrast, asymmetric autocatalysis is an automultiphcation of a chiral compound P, in which the chiral product P acts as a chiral catalyst P for its own production/ ... 

Kreis P, Mosandl A (1992) Chiral compounds of essential oils XI Simultaneous stereoanalysis of Lavandula oil constituents. Flavour Fragr 17 187... 

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